1. Field of the Invention
The present invention relates generally to thermal analysis methods and apparatus. More specifically, the present invention relates to static and dynamic thermomechanical analysis of localized regions of inhomogeneous samples that are identified and selected at high spatial resolution using scanning probe microscopy.
2. Description of the Related Art
Techniques for the thermomechanical characterization of solids and thin films are well-known and widely used. A description of such methods is given in "Thermal Analysis--Techniques and Applications" by E. L. Charsley and S. B. Warrington (eds.), Royal Society of chemistry, Cambridge, England (1992), which is hereby incorporated by reference in its entirety herein. There are several problems with these methods.
One problem is a practical one. Conventional thermomechanical or dynamic mechanical analysis experiments are often very time consuming, typically requiring several hours to complete. Consequently, solutions to urgent problems in industry are often delayed.
Another problem is related to sampling or data collection. Frequently, the sample being analyzed is either too small or too thin, or it is buried within a larger component from which it is difficult or impossible to extract. For example, the problems associated with obtaining a sufficient sample of a thin film that is firmly adhered to a substrate or sandwiched between two other layers are well-known.
Another problem is more fundamental in nature. Thermal methods are particularly useful in studying the morphology of polymer and polymer-containing samples. Modulated Temperature Differential Scanning Calorimetry (MTDSC), which was developed several years ago by Reading and co-workers, has greatly increased the quality of the structural information that can be obtained by calorimetry. See, M. Reading in Trends in Polymer Science vol. 1 pp. 248-53 (1993) and U.S. Pat. No. 5,224,775 to Reading et al. (the "'775 patent"), both of which are hereby incorporated by reference in their entirety herein. One advantage of MTDSC is that `reversing` and `non-reversing` processes can be separated. A second advantage of MTDSC is the improvement in the sensitivity and resolution with which glass transitions can be measured. As a result, scientists have found that MTDSC offers unique benefits in the study of curing systems, semi-crystalline polymers, and, in particular, polymer blends and related systems. But, even this advanced method cannot give spatially resolved information.
Moreover conventional thermomechanical analysis is performed using bulk samples, and consequently does not provide spatially resolved data. The inability of conventional thermal analytical techniques to give spatially resolved information is a critical shortcoming because modern polymeric materials are usually blends or composites with complex morphologies whose evaluation is crucial to the determination of their material properties. But, conventional thermal analysis techniques provide no information regarding the size of the domains or how they are distributed in space.
Therefore, it would be advantageous to use the advantages offered by each of the techniques described above and others described below by incorporating them into a technique for localized thermomechanical and calorimetric analysis, together with high-resolution microscopy.